The following abbreviations and terms are herewith defined, at least some of which are referred to within the following description of the present disclosure.    3GPP 3rd-Generation Partnership Project    AB Access Burst    AGCH Access Grant Channel    ASIC Application Specific Integrated Circuit    BLER Block Error Rate    BSS Base Station Subsystem    BTS Base Transceiver Station    CC Coverage Class    CN Core Network    EC Extended Coverage    EC-GSM Extended Coverage Global System for Mobile Communications    EC-PACCH Extended Coverage Packet Associated Control Channel    EC-PDTCH Extended Coverage Packet Data Traffic Channel    EC-RACH Extended Coverage Random Access Channel    eNB Evolved Node B    EDGE Enhanced Data rates for GSM Evolution    EGPRS Enhanced General Packet Radio Service    ESAB Extended Synchronization Access Burst    E-UTRA Evolved Universal Terrestrial Radio Access    FN TDMA Frame Number in GSM    GSM Global System for Mobile Communications    GERAN GSM/EDGE Radio Access Network    GPRS General Packet Radio Service    HARQ Hybrid Automatic Repeat Request    IoT Internet of Things    IQ In-phase/Quadrature    LTE Long-Term Evolution    MCL Maximum Coupling Loss    MCS Modulation and Coding Scheme    MF Multi-Frame    MME Mobility Management Entity    MS Mobile Station    MTC Machine Type Communications    NB Node B    PACCH Packet Associated Control Channel    PDCH Packet Data Channel    PDN Packet Data Network    PDTCH Packet Data Traffic Channel    RACH Random Access Channel    RACH11 11 bit RACH coding scheme for legacy RACH and EC-RACH CC1/2/3/4    RACH11′ 11 bit RACH coding scheme for CC5 2TS EC-RACH    RAN Radio Access Network    RAT Radio Access Technology    SGSN Serving GPRS Support Node    TDMA Time Division Multiple Access    TS Time Slot    TSC Training Sequence Code    TSG Technical Specification Group    UE User Equipment    UL Uplink    WCDMA Wideband Code Division Multiple Access    WiMAX Worldwide Interoperability for Microwave Access
Coverage Class (CC): At any point in time a wireless device belongs to a specific uplink/downlink coverage class that corresponds to either the legacy radio interface performance attributes that serve as the reference coverage for legacy cell planning (e.g., a Block Error Rate of 10% after a single radio block transmission on the PDTCH) or a range of radio interface performance attributes degraded compared to the reference coverage (e.g., up to 20 dB lower performance than that of the reference coverage). Coverage class determines the total number of blind transmissions to be used when transmitting/receiving radio blocks. An uplink/downlink coverage class applicable at any point in time can differ between different logical channels. Upon initiating a system access a wireless device determines the uplink/downlink coverage class applicable to the RACH/AGCH based on estimating the number of blind transmissions of a radio block needed by the BSS (radio access network node) receiver/wireless device receiver to experience a BLER (block error rate) of approximately 10%. The BSS determines the uplink/downlink coverage class to be used by a wireless device on the assigned packet channel resources based on estimating the number of blind transmissions of a radio block needed to satisfy a target BLER and considering the number of HARQ retransmissions (of a radio block) that will, on average, be needed for successful reception of a radio block using that target BLER. Note: a wireless device operating with radio interface performance attributes corresponding to the reference coverage (normal coverage) is considered to be in the best coverage class (i.e., coverage class 1) and therefore does not make any additional blind transmissions subsequent to an initial blind transmission. In this case, the wireless device may be referred to as a normal coverage wireless device. In contrast, a wireless device operating with radio interface performance attributes corresponding to an extended coverage (i.e., coverage class greater than 1) makes multiple blind transmissions. In this case, the wireless device may be referred to as an extended coverage wireless device. Multiple blind transmissions corresponds to the case where N instances of a radio block are transmitted consecutively using the applicable radio resources (e.g., the paging channel) without any attempt by the transmitting end to determine if the receiving end is able to successfully recover the radio block prior to all N transmissions. The transmitting end does this in attempt to help the receiving end realize a target BLER performance (e.g., target BLER≤10% for the paging channel).
Extended Coverage: The general principle of extended coverage is that of using blind transmissions for the control channels and for the data channels to realize a target block error rate performance (BLER) for the channel of interest. In addition, for the data channels the use of blind transmissions assuming MCS-1 (i.e., the lowest modulation and coding scheme (MCS) supported in EGPRS today) is combined with HARQ retransmissions to realize the needed level of data transmission performance. Support for extended coverage is realized by defining different coverage classes. A different number of blind transmissions are associated with each of the coverage classes wherein extended coverage is associated with coverage classes for which multiple blind transmissions are needed (i.e., a single blind transmission is considered as the reference coverage). The number of total blind transmissions for a given coverage class can differ between different logical channels.
Internet of Things (IoT) devices: The Internet of Things (IoT) is the network of physical objects or “things” embedded with electronics, software, sensors, and connectivity to enable objects to exchange data with the manufacturer, operator and/or other connected devices based on the infrastructure of the International Telecommunication Union's Global Standards Initiative. The Internet of Things allows objects to be sensed and controlled remotely across existing network infrastructure creating opportunities for more direct integration between the physical world and computer-based systems, and resulting in improved efficiency, accuracy and economic benefit. Each thing is uniquely identifiable through its embedded computing system but is able to interoperate within the existing Internet infrastructure. Experts estimate that the IoT will consist of almost 50 billion objects by 2020.
MTC device: A MTC device is a type of device where support for human interaction with the device is typically not required and data transmissions from or to the device are expected to be rather short (e.g., a maximum of a few hundred octets). MTC devices supporting a minimum functionality can be expected to only operate using normal cell contours and as such do not support the concept of extended coverage whereas MTC devices with enhanced capabilities may support extended coverage.
At the 3rd-Generation Partnership Project (3GPP) Technical Specification Group (TSG) Radio Access Network (RAN) Meeting #73, a Work Item (WI) on “Radio Interface Enhancements for EC-GSM-IoT” was approved (see RP-161806 entitled “New WID on Radio Interface Enhancements for EC-GSM-IoT”; Source: Nokia, Alcatel-Lucent Shanghai Bell, ORANGE, Ericsson L M, Sierra Wireless S. A., MediaTek Inc.; New Orleans, U.S.A.; 19-22 Sep. 2016 (hereinafter “RP-161806”)—the entire contents of this document are hereby incorporated herein by reference for all purposes). One of the WI objectives was:
Maximum Coupling Loss (MCL) improvement targeting at least 3 dB for low power devices (i.e., 23 dBm) on all uplink channels.
It is further stated that the following would be considered:
New coverage class (CC) for uplink channels to improve the coverage performance of low power devices including at least:                design of new channel coding schemes for the EC-PDTCH and EC-PACCH uplink channels with increased number of blind physical layer transmissions with allocation in 2 and 4 consecutive PDCHs.        definition of an increased number of blind physical layer transmissions for 2TS EC-RACH, investigation on modified channel coding and alternative burst types with predefined longer synchronization sequences for improved coverage performance for the EC-RACH channel.        
The following is a discussion about the state-of-the-art involving a Coverage Class 4 (CC4) 2TS EC-RACH which uses a legacy access burst 100 (AB 100) configured as illustrated in FIG. 1 (PRIOR ART). As shown, the legacy access burst 100 consists of 8+3 tail bits 102, 41 synchronization bits 104, 36 payload bits 106 (36 encrypted payload bits 106), and a guard period of length 68 bits 108. The legacy access burst 100 uses 48 blind physical layer transmissions over 1 or 2 time slots (TSs) to achieve the Maximum Coupling Loss (MCL) performance target defined in Release 13 (R13) of 3GPP Technical Specification (TS) 45.002 V.13.5.0 (Mar. 20, 2017) entitled “GSM/EDGE Multiplexing and multiple access on the radio path” (hereinafter “3GPP TS 45.002”) (the entire contents of this document are hereby incorporated by reference herein for all purposes).
The 36 encrypted payload bits 106 of the legacy access burst 100 are generated by using a coding scheme (known as RACH11) designed for CC4 2TS EC-RACH which is shown below in TABLE 1.
TABLE 1Channel coding design for CC4 2TS EC-RACHPayload bits11 bitsParity 6 bitsConvolution coding1/3 convolutional codingNumber of data bits after channel36 bitscoding and puncturing
In an attempt to improve the performance of the above-described CC4 2TS EC-RACH, several papers have been published including: (1) R6-160159 entitled “Radio interface enhancements for EC-GSM-IoT—New access burst formats”, source Ericsson LM, 3GPP TSG RAN Working Group (WG) 6 Meeting #2; Reno, Nev., U.S.A.; 14-18 Nov. 2016 (hereinafter “R6-160159”); (2) R6-160193 entitled “UL MCL Improvement for Low Power Devices in EC-GSM-IoT—Concept Overview”, source Nokia, 3GPP TSG RAN WG6 Meeting #2; Reno, Nev., U.S.A.; 14-18 Nov. 2016 (hereinafter “R6-160193”); and (3) R6-160176 entitled “UL MCL Improvement for Low Power Devices in EC-GSM-IoT Performance Evaluation”, source Nokia, 3GPP TSG RAN WG6 Meeting #2; Reno, Nev., U.S.A.; 14-18 Nov. 2016 (hereinafter “R6-160176”) (the entire contents of these three documents are hereby incorporated by reference herein for all purposes). The solutions presented in these papers for improving the performance of the CC4 2TS EC-RACH and the associated problems therewith are briefly discussed hereinafter.    Option 1: Only increase the number of blind physical layer transmissions            As can be seen from FIG. 2 (PRIOR ART) which was disclosed in the aforementioned Technical Document (Tdoc) R6-160159 of the 3GPP TSG RAN WG6 Meeting #2, the processing gain was initially increased when the number of transmissions is increased. However, at a higher number of transmissions, the actual experienced processing gain deviates more and more from the ideal gain.            Option 2: Extend the length of the access burst sent using timeslots 0 and 1, thereby allowing for an increased number of synchronization sequence bits while also increasing the number of physical layer transmissions.            As is discussed in Tdoc R6-160159 (see reference above), increasing the length of the burst will directly improve the phase shift estimation through an increased processing gain, and increasing the length of the synchronization sequence will improve the detection of the sync position of the burst, which is expected to improve the phase shift estimation and therefore the processing gain.        However, further simulation also showed that the experienced processing gain resulting from further increasing the number of synchronization sequence bits is limited above a certain synchronization sequence length.            Option 3: Extend the length of the access burst sent using timeslots 0 and 1, but repeat the data parts for the portion of the access burst sent on Time Slot 0 (TS0) while increasing the number of physical layer transmissions.            This solution has been described and evaluated in the aforementioned Tdoc R6-160193 and the aforementioned Tdoc R6-160176, both from the 3GPP TSG RAN WG6 Meeting #2. The drawback with this approach is that it increases the complexity of the signal accumulator in the receiver as well as creating, to some extent, interference to the CC4 2TS EC-RACH.        Moreover, there will also be multiple demodulation points at the demodulation positions for the proposed coverage class 5 (CC5) 2TS EC-RACH discussed in Tdoc R6-160193 (see reference above), which will require additional processing as well as local data memory for the signal processor in the receiver in a short time.        In addition, based on the simulations, the performance gain shown in Tdoc R6-160176 (see reference above) is limited to 4 dB when a total of 75 physical layer transmissions (150 bursts) is used, thus making it the limiting channel for the coverage enhancements targeted by RP-161806 (see reference above) for the EC-PDTCH, EC-PACCH and EC-RACH. Ideally, the number of physical layer transmissions should be kept as low as possible since it directly impacts the power consumption.        Finally, the length of information data bits in Tdoc R6-160193 (see reference above) is reduced from 11 bits (EC-RACH CC4) to 10 bits, which means that no extra bits are available for future use.        
As can be seen there is still a need to address the problems associated with the state-of-the-art approaches in order to improve the coverage performance of the EC-RACH. The present disclosure addresses these problems while improving the coverage performance of the EC-RACH.